Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J161/00—Adhesives based on condensation polymers of aldehydes or ketones; Adhesives based on derivatives of such polymers
  • C09J161/20—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
  • C09J161/22—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds
  • C09J161/24—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds with urea or thiourea
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J159/00—Adhesives based on polyacetals; Adhesives based on derivatives of polyacetals
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
  • C08L2666/04—Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L59/00—Compositions of polyacetals; Compositions of derivatives of polyacetals

Definitions

• the present invention relates to field of urea formaldehyde adhesive systems for manufacturing of glued products, where the emission of formaldehyde from the glued product is substantially reduced compared with prior art urea formaldehyde adhesives. More specifically, the invention relates to a modified adhesive system and to a modifier for urea formaldehyde adhesive systems.
• Amino resins such as urea formaldehyde (UF) 5 modified UF and melamine urea formaldehyde (MUF) adhesive systems have been used for decades for gluing of wood based products. These amino resins are used in foliation, veneering, production of MDF, HDF and chipboards, and laminated products, e.g. parquet, furniture boards, solid wood laminates, plywood, curved plywood etc.
• the composition of the adhesive system is adjusted to meet the criterions for the actual product, such as the quality of the glue line, in addition to economical and practical factors, such as the cost of the adhesive /adhesive system, pot life, assembly time and pressing/hardening time.
• Formaldehyde based adhesives will release varying amounts of formaldehyde during production of the glue and during production of the glued products. There will also be some formaldehyde emission from the finished glued product. There are strict regulations on the formaldehyde concentration in working environments and in the living areas (indoor air quality). Maximum limits for emission of formaldehyde in productions facilities and from the glued products are set by different authorities. Accordingly, a substantial effort has been done by several actors in research and in the adhesive industry to reduce the emission of formaldehyde in the production of wooden products and from glued wooden products, without unacceptable increase in cost or loss of quality in the glued products.
• a adhesive having a low F:U ratio will normally result in a glue line that is more brittle than an adhesive having a higher ratio, lower quality of gluing, i.e. a higher degree of gluing defects, reduced water resistance and reduced strength as well as reduced shelf life of the adhesive. Additionally, a reduction of the F:U ratio results in a reduction of the reactivity of the adhesive, resulting in a prolonged curing time.
• higher press temperature or addition of more acid or acidic components are necessary. A long curing time, and correspondingly long pressing time, is unwanted as it results in a lower production capacity of a plant. Higher pressing temperatures are unwanted due to higher energy costs and due to the increased risk of the glued product becoming more unstable (more curved). Increased addition of acid/acid components is unwanted since the increased the reactivity of the adhesive system not only shortens the curing speed but also reduces the pot life and assembly time of the system.
• An alternative to reduction of the ratio F:U in the adhesive is to add scavengers binding free formaldehyde that is released during the curing of the adhesive. Depending on the type and amount of scavenger added, it can also bind free formaldehyde during the lifetime of the glued product.
• WO 02/0723244 which is incorporated as reference, a method of reducing formaldehyde emission from a laminated wooden product glued with UF adhesive is described. At least one of the surfaces to be glued is in a separate step treated with a solution comprising an ammonium salt, before the adhesive is applied.
• Ammonium salts are known to react with free formaldehyde to bind the formaldehyde in a nonvolatile form.
• the ammonium salt solution may additionally comprise urea to improve the formaldehyde scavenging effect of the treatment. This method does, however, require an additional process step, adding cost to the finished product.
• Resorcinol and resorcinol derivatives are known to bind formaldehyde.
• GB 589,131 which is incorporated as reference, describes the use a formaldehyde fixing agent, such as resorcinol, in a urea formaldehyde resin to avoid premature hardening.
• Resorcinol is here used to bind formaldehyde that is released from the urea formaldehyde condensation product to avoid a reaction between the ammonium that that is used as a hardener, and free formaldehyde to liberate acid that will initiate hardening of the resin.
• An objective of the present invention is to provide a low formaldehyde emission urea formaldehyde based adhesive system for gluing of laminated wood based products. It is also an objective that the formaldehyde emission is low during the use of the adhesive system, and that the emission from the glued products is at very low levels. It is also an objective that the adhesive system fulfills practical requirements set by the industry using the adhesives and the requirements for gluing quality.
• the present invention relates to an adhesive system comprising the following parts: a) a urea formaldehyde resin adhesive part; b) a hardener part comprising one or more curing agents(s), c) a polymer dispersion; and d) a formaldehyde scavenger, wherein part d) comprises a combination of urea and resorcinol.
• a formaldehyde scavenger comprises a combination of urea and resorcinol.
• the adhesive system consists of two components: i) an adhesive component comprising part a), ii) a hardener component comprising part b), part c) and part d).
• Component ii) of a two component system may also comprise an additional carboxylic acid part e).
• the carboxylic acid improves the gluing quality and the water resistance of the glue line.
• the adhesive system comprises three components: i) an adhesive component comprising part a); ii) a hardener component comprising part b), and parts of part c), and iii) a modifying component comprising at least parts of part d) and parts of part c).
• Component ii) or component iii) of a three component system may also comprise an additional carboxylic acid part e).
• the carboxylic acid improves the gluing quality and the water resistance of the glue line.
• part c) is a functionalized PVAc.
• the present invention relates to a formaldehyde scavenger for urea formaldehyde adhesive systems for reduction of formaldehyde emission from the glued products, wherein the formaldehyde scavenger comprises urea and resorcinol.
• the formaldehyde scavenger comprises a polymer dispersion.
• the scavenger additionally comprises a carboxylic acid, preferably lactic acid.
• the polymer dispersion comprises a functionalized PVAc.
• the present invention relates to a process for the manufacture of an adhesive system comprising parts (a) to (d) descirbed above, said process comprising the steps of providing a first component i) comprising parts a), and a second component ii) comprising part b) and at least parts of part (c), wherein the ingredients urea and resorcinol of part d) are added together or separately to the second component ii), and/or are provided as a third component iii) together with at least parts of part c).
• parts and percentages are given in weight parts and % by weight, respectively, if not specifically indicated otherwise.
• a UF adhesive system comprises two components, an adhesive component and a hardener component.
• the adhesive system according to the present invention may be provided as a three component adhesive system, or a two component system.
• the present adhesive system comprises several parts that are combined into a two or three component adhesive system.
• the parts of the adhesive system are: a) an urea formaldehyde resin adhesive part, b) a hardener part, c) a polymer dispersion part, d) an urea formaldehyde scavenger part, and optionally e) a carboxylic acid part.
• the adhesive part of the present adhesive system is a urea formaldehyde (UF) or a modified UF adhesive.
• the adhesive part has preferably a content of solids from about 65 % to about 75 %.
• a preferred adhesive has content of solids of about 68-73%.
• the adhesive part has a viscosity at 25 °C from about 500 to 10000 mPas, preferably from about 1000 to 4000 mPas, all for a freshly prepared adhesive, depending on the specific use.
• a specially preferred adhesive has a viscosity at 25 °C of 2500 to 3200 mPas.
• the molar ratio of formaldehyde to urea (F/U) in an unmodified UF adhesive is preferably in the range from 1,5 to 1,1.
• a preferred UF adhesive has a molar ratio of about 1,25 to 1,35. In a modified UF adhesive the molar ratio may be higher, e.g. up to about 2.0:1 b)
• the hardener part of the adhesive system comprises a liquid in which one or more acid(s), acid salt(s) and /or acid generating salt(s) as active component(s) are dissolved.
• the liquid in which the components are dissolved is water.
• the selection of acid(s), acid salt(s) or acid generating salt(s) primarily depends on the desired characteristics for the hardener, such as how quickly it is desired that the curing takes place after the hardener and the adhesive are brought together.
• Non-limiting examples of preferred acids are phosphoric acid, sulfamic acid, maleic acid, citric acid, formic acid and para-toluene sulphonic acid
• Acid salts are in the context of the present invention salts that results in an acidic solution when they are dissolved in water.
• Non-limiting examples of acid salts are aluminium nitrate, aluminium sulphate and aluminium chloride.
• Acid generating salts in the context of the present invention are salts that react with formaldehyde in the adhesive to generate an acid.
• Non-limiting examples of acid generating salts are ammonium salts, such as ammonium phosphates, ammonium sulphate and ammonium chloride.
• the hardener may have a pH in the range from 0 to 4, preferably from 0.5 to 3.0. To obtain the preferred characteristics, the hardener has to include an acid and an acid salt, an acid and an acid generating salt, or an acid generating salt and an acid salt. The hardener may also comprise an acid in combination with both an acid generating salt and an acid salt. The hardener may also comprise more than one acid, more than one acid generating salt and/or more than one acid salt.
• the active ingredients in the hardener are combined in amounts to give the required reactivity and stability of the hardener.
• the reactivity is determined by the total amounts of acid, acid salts and acid generating salts.
• the skilled man in the art has the knowledge how to achieve both the required reactivity and the required stability.
• the relative amounts of the ingredients are often adjusted to the costumers needs.
• the dispersions used in the present invention is preferably a water based dispersion selected among vinyl adhesives, polyurethane and / or polyacrylate and may comprise one of the mentioned polymers or as a mixture of more than one of the mentioned . polymers.
• the polymers have preferably a molecular weight in the range from about 2000 to about 20000, have a viscosity in the range from 5000 to 40000 mPa*s, more preferably from about 10000 to about 25000 at 23 0 C, and the dispersion preferably has a content of solids from 45 to 65 % by weight.
• polyvinylacetate dispersion it has been found to especially preferable to use a polyvinylacetate dispersion.
• PVAc is functionalised.
• Partly functionalized polymer dispersion may be obtained as such from the supplier or be prepared by mixing two or more polymer dispersions. Preferably, 40 to 100% of the polymer dispersion is functionalized.
• polymer comprises post polymerisation cross-binding groups that may cross-bind with each other or with other ingredients of the adhesive during the curing.
• Cross-binding groups may be introduced into vinyl adhesives by introducing small amounts of reactive monomers such as N-methylolacrylamide or triallylcyanurate, to be polymerised with the vinyl adhesive.
• reactive monomers such as N-methylolacrylamide or triallylcyanurate
• Polyvinylacetate (PVAc) ethylenevinylacetate and polyvinylpropionate are examples on preferred vinyl adhesives.
• Preferred polymer dispersion may be emulsion adhesives, e.g. the emulsion adhesives described in US Patent No. 5.545.684.
• This polymer dispersion has a pH in the range 2 to 6 and comprises at least one homo- or co-polymer polyvinyl ester, and at least one polymer protective colloid.
• the copolymer Specially preferred as the copolymer are the copolymers that includes N-functional groups, such as (meth)arylamide, allylcarbamate, acrylonitrile, N- methylol(meth)acrylamide, N-methylolallylcarbamate, alcyl ethers and Mannich bases of N-methylol(meth)acrylamide and N-methylolallylcarbamate etc. It is preferred that the amount of these monomers is less than 15% of weight of the total amount of monomers.
• the inclusion of polymer dispersion in the adhesive system improves the performance of the adhesive as it improves the characteristics of the hardened adhesive and the adhesive quality.
• the UF scavenging part comprises urea and resorcinol.
• Urea is added as a formaldehyde scavenger.
• urea is a known formaldehyde scavenger that in effect reduces the F:U ratio.
• Earlier tests performed by the applicant have shown that addition of urea in the adhesive results in undesirable effects. Addition of urea to the adhesive immediately before application of the adhesive results in fewer undesirable effects than addition of urea to the adhesive before delivery to the costumer. Additionally, it has been surprisingly found that addition of urea together with resorcinol and polymer dispersion results in a lower degree of unwanted effects than addition of urea alone.
• the amount of urea preferably constitutes from about 1 to about 15 % by weight of the adhesive system, more preferably from about 3 to about 10 % by weight.
• urea is preferably mixed with the adhesive part shortly before, such as the same day, or during the application of the adhesive to the substrate to be glued.
• addition of urea is known to reduce the reactivity of a UF adhesive system.
• the present inventors have also surprisingly found that this effect is substantially reduced if urea is combined with the UF resin immediately before use of the adhesive system, i.e. within the same day or within a few hours to a few minutes before application.
• Resorcinol is added both as a formaldehyde scavenger and to improve the performance of the cured adhesive.
• resorcinol and resorcinol derivatives are known as formaldehyde scavengers, additionally resorcinol is known as a fortifier for UF and MUF adhesives.
• the amount of resorcinol in the adhesive system is preferably from about 1 to about 15 % by weight, more preferably from about 3 to about 10 % by weight of the adhesive system.
• the present inventors have found that the formaldehyde scavenging effect of resorcinol is reduced during storage of an aqueous solution of UF resin and resorcinol.
• resorcinol is known to reduce the reactivity of a UF adhesive system.
• the present inventors have also surprisingly found that this effect is substantially reduced, and addition of resorcinol may even increase the reactivity of the adhesive system, if resorcinol is combined with the UF resin immediately before use of the adhesive system, i.e. within the same day or within a few hours to a few minutes before application.
• the optional carboxylic acid is added to improve the properties of the glue line and to stabilize the modifier or hardener to improve the shelf life thereof.
• useful carboxylic acids are formic acid, acetic acid, and lactic acid. Lactic acid is a preferred carboxylic acid as it is odorless. If higher reactivity is required, other acids may be preferred.
• the amount of acid may vary depending on the choice of other components, the choice of acid and the wanted reactivity of the adhesive system. The amount of acid may vary from 0 to about 3 % by weight, preferably from about 1 to about 2 % by weight of the adhesive system.
• the carboxylic acid may be included in the hardener part or in a separate modifier part.
• the adhesive system is made by combining the parts a) to d) and optionally part e) into a two or three component adhesive system depending on the user's demands and/or preferences.
• the preferences and/or demands of the user may be determined by the method for application of the adhesive system, the required pot life for the adhesive system or mixture of the parts of the adhesive system, the required reactivity of the adhesive system etc.
• the skilled man in the art will understand that the ingredients of the different parts have to be selected to the intended use and the intended combination of parts to avoid any unwanted reactions or incompatibility between components after mixing the parts a) to e) into the components of the adhesive system.
• a two component adhesive system consists of two components; i) an adhesive component, and ii) a hardener component.
• the adhesive component i) comprises part a), and the hardener component comprises the parts b) to d) and optionally part e).
• a three component system adhesive system consists of three components; i) an adhesive component, ii) a hardener component, and iii) a modifying component.
• the adhesive component i) preferably comprises part a), the hardener component b) preferably comprises part b) and parts of part c), whereas the modifying component iii) preferably comprises part d) in addition to parts of part c).
• An optional carboxylic part c) may be included in the hardener component ii) or in the modifying component iii).
• a separate modifying component iii) makes it possible for the user to purchase standard adhesive and hardener, and modify the system for specific uses by means of different modifying components iii) having different concentration of the components described herein.
• some of the ingredients may be included in more than one component i) to iii). As indicated above parts of part c) may be included both in component ii) and iii) in a three component system. Additionally, parts of the urea and/or resorcinol may be added to the hardener component ii) of a three component system to avoid increasing the volume of the modifying component iii). The optional carboxylic acid part e) may be added to either the hardener component ii) or the modifying component iii) in a three component system. Both a two and three component system may be applied to the surfaces to be glued separately or premixed. A two component system may be applied by separate application of both components by means of any of the methods for separate application that are known for the skilled man in the art, or may be premixed and applied by any known method for application of a one component or premix adhesive system.
• a three component system may be applied to a substrate by separate application of all three components, by premixing component i) and component iii) and apply the resulting adhesive system as a two component system comprising a hardener component ii) and the combined component i) and iii).
• a three component adhesive system may also be premixed by mixing all components i), ii) and iii) and apply the resulting mixture to the substrate.
• the concentration of the different ingredients of the parts a) to e) in the total adhesive system is of vital importance.
• the concentration of the ingredients in the different components has to sufficient to give the intended resulting concentration adhesive mixture.
• the preferred concentration of the different ingredients in the adhesive system is given above under the discussion of the part a) to e).
• the polymer dispersion, or parts thereof, may also be added to the hardener.
• the polymer dispersion and the adhesive part can be mixed, but the shelf life of such mixtures are short hence it is not a viable solution. It is therefore preferred that the modifier is added to the adhesive part by the user immediately before application, and not before delivery.
• the three component system may be applied as three separate components e.g by application of strings.
• the hardener is usually applied firstly.
• the layer of hardener applied to the substrate has to be thin. Accordingly, the volume of the hardener part has to be low.
• the modifier may alternatively be mixed with the adhesive part before the application. To avoid unwanted reactions between the adhesive component i) and the modifier component iii), the mixing of the two parts is preferably performed immediately before application. Immediately before application is here intended to mean within a few minutes to a few hours before application.
• the gluing quality according to durability class C3 was tested. This test comprises three conditioning sequences, dry, cold water and warm water. In all tests the adhesive strength was measured in N/mm 2 .
• samples were conditioned for 7 days in standard atmosphere (20+2 °C and 65+5% relative humidity) before measurement of the adhesive strength.
• the samples were conditioned for 7 days in standard atmosphere and thereafter immersed for one day in water at 20+5 °C before measurement of adhesive strength.
• the samples were conditioned for 7 days in standard atmosphere and thereafter immersed for three hours in water at 67 ⁇ 2 0 C and then cooled down for two hours in water at 20 ⁇ 5 0 C, before measurement of adhesive strength.
• the requirements for the durability class C3 are an adhesive strength of > 10 N/mm 2 in the dry test, > 7 N/mm 2 in the cold water test and > 4 N/mm 2 in the warm water test.
• test samples were placed back to back, edge sealed as described in the standard, wrapped airtight, and shipped to Dansk Teknologisk Institutt (DTI) for testing according to EN 717-1.
• the area of the test specimens were corresponding to a total loading rate (i.e.
• test sample surface area excluding the are of the edges to the volume of the chamber in m 2 /m 3 ) of 1 m 2 /m 3 , and placed in a chamber having a volume of 225 liters, at 23+0,5 °C, at a humidity of 45 ⁇ 3% RH, with an air exchange rate of once per hour, for 9 or 21 days, respectively.
• the steady state formaldehyde concentration in the chamber obtained under these conditions was measured by drawing air from the chamber through washing bottles containing water absorbing the formaldehyde.
• the formaldehyde content of the aqueous solutions was measured photometrical by the acetyl acetone method, to give results in mg/m 3 .
• the requirements for an El classification according to EN 717-1 is an emission lower than 0,124 mg/m 3 .
• Un-lacquered test samples was cut and placed in a desiccator together with a dish with distilled water, in the applicant's conditioning room at a temperature of 20+0,2 °C.
• the amount of formaldehyde absorbed by the distilled water was determined by the acetyl acetone method to give results in mg/1.
• the mean value for formaldehyde emission from parallel test must not exceed 0,3 mg/1, and no single result may be higher than 0,4 mg/1.
• the gluing quality was assessed by inserting a knife into a glue line to split the surface layer from the core layer. The resulting fracture surface was visually inspected and fracture of the wood of the core layer vs. fracture in the glue line as such was assessed by visual inspection of the fracture and the glue line. Results are given in % wood fracture, where 100 % wood fracture indicates a glue line of good quality as there is no fractures in the glue line as such.
• Test samples of three layered parquet cut a size of 75x75 mm were immersed in hot water at temperatures of 70 ⁇ 3 °C for 2 hours and dried in an oven at a temperature of
• Test samples of three layered parquet cut a size of 75x75 mm were immersed in water at temperatures of 35 ⁇ 3 0 C for 2 hours and dried in an oven at a temperature of 60 ⁇ 3 0 C for three hours before the glue line was investigated for delamination.
• CEN European Committee for Standardization
• test specimens were positioned in the shearing tool and a shearing force was applied parallel to the adhesive line.
• the maximal load at failure was noted and shear strength was calculated in N/mm 2 . Additionally, the % wood failure was calculated.
• the lower 5 -percentile of the shear strength calculated in accordance with EN 326-1 shall not be less than 08 N/mm2.
• the mean percentage wood failure of each panel shall be more than 40%
• Example 1 which was performed in the applicant's laboratory, all the tests in the Examples were performed in a regular production line.
• present invention will be further described by means of the following non-limiting examples. Even though only a limited field of use for the present adhesive system and modifier is described, the skilled man in the art will understand that the present gluing system and modifier may be used for different gluing operations and for production of different kind of products.
• the present gluing system and modifier may thus be used for foliation of wood based products, veneering, in addition to different kinds of lamination, such as production of parquet, plywood, curved plywood, solid wood lamination, and production of beams.
• the application method for adhesive and hardener is indicated for all examples.
• the modifier was mixed with the adhesive as indicated in each example.
• the substrates to be tested are described in the examples, however, for the examples relating to laminated parquet boards, the boards have a total thickness of 14 mm, comprising a 4 mm surface layer of hardwood, a 8 mm spruce core layer, and a 2 mm spruce backing veneer.
• the test specimens were produced as 5 layered lamella parquet having a 10 mm surface layer in the middle, a core layer at each side of the surface layer and a backing veneer at each side. After gluing the surface layer was split and planed to give two laminated parquet boards.
• the surface layer was made of beech, oak or merbau, as indicated in the examples.
• test samples After application of adhesive and hardener, the test samples were layered to build up the layered structure as described above for parquet, and introduced to a radio frequency (RF) lamination press where the test specimens were heated by means of high frequency electric power.
• RF time The heating time is given in the tables below as “RF time”.
• Post-curing time The time after application of heat before the pressure is released and the test specimen is removed from the press, is in the tables referred to as "Post-curing time".
• composition of the modifiers and hardeners are given in the following tables 1 and
• Gluing tests with hardeners with different resorcinol content were performed to see how much of the relatively expensive resorcinol that had to be added to the adhesive mixture. Additionally, the effect of addition of lactic acid was tested.
• the mixture of adhesive and any modifier was mixed with hardener before application of about 150 g/m 2 on one side. After a closed assembly time of 2 minutes the test specimens were pressed in a hot press at 100 °C and a pressure of 10 kp/cm 2 .
• the adhesive Prefere® 4108 was used for all tests.
• the modifier, the hardener and the parts of each mixture, are given in table 3 below, whereas the results from the shear strength test according to EN 12765, are given i table 4 below.
• Prefere® 4108 a urea formaldehyde adhesive
• Prefere ® 5100 hardener (hardener A) is a standard glue system used for production of parquet by RF pressing. The following example will describe a standard gluing process using this glue system.
• the adhesive and hardener are applied by means of rollers for separate application. Typical values for adhesive and hardener application spread are given in the table below.
• the necessary heating time (RF time) and pot curing time depend on the RF press used as well as the wood species of the surface layer. Typical values for the RF press used in the examples in the present description are also given in the table below as well as typical surface temperatures of the different wood species after coming out of the press.
• Table 7 illustrates that the wood itself will emit some formaldehyde and the level of this emission. It also shows that lacquering reduces the emission.
• Use of different wood species as surface layer, core layer and backing veneer will have an effect on the formaldehyde emission from the finished parquet. This is due to differences in the formaldehyde content of the wood species as well as the ease of which formaldehyde penetrates though the different wood species. Less formaldehyde will penetrate through a surface layer of a high density wood species compared to a low density wood species.
• a gluing test was performed using Prefere® 4108 a urea formaldehyde adhesive, and harderer B (part 1 of the test).
• a further gluing test was done using Prefere 4108 pre- mixed with modifier 2 and hardener C (part 2 of the test).
• the mixing ratio of Prefere 4108 and modifier 2 was 100 parts by weight to 18,5 parts by weight.
• the test was performed in the same production equipment as used in Example 2.
• the parquet made in these tests had beech surface layer.
• the adhesive, or adhesive pre-mix in case of test 2, and hardener were applied by means of rolls for separate application.
• the application was about 140-150 g/m 2 of adhesive and about 20-25 g/m 2 of hardener.
• the heating time (RF time) in the press was 22 seconds, and the post heat curing time was 10 seconds for test 1 and 24 sec. RP time and 10 sec. post heat curing time in test 2.
• the second specimen, specimen B was picked out from part 2 of the test for test of bond quality and emission testing (chamber emission test and test according to JANS 16) of lacquered and un-lacquered specimens.
• test specimens A and B had lower formaldehyde emission than the standard system, a result that was expected due to the inclusion of urea as a formaldehyde scavenger.
• Test specimen B had, however, test results both for formaldehyde emission and gluing quality that was substantially better than for test specimen A.
• resorcinol seemed to improve both gluing quality and formaldehyde emission and seemed to be necessary to fulfill the requirements both for gluing quality that are demanded by the costumers and the requirements to reduce the formaldehyde emission.
• the adhesive system including resorcinol was therefore the preferred system, even if resorcinol is expensive and adds cost to the adhesive system.
• Tests were performed using Prefere® 4108 adhesive, modifier 1 and hardener A. Additional test was performed using modifier 5 where PVAc is substituted by an organic filler known to give good gluing, Bonit® (Wetzel GmbH & Co KG, Germany), and water.
• hardener A having a lower reactivity than the hardener C used in Example 4, was used.
• the surface layer was made of beech, oak or merbau, as indicated in the tables.
• the hardener application was 25-30 g/m 2 and the glue application was 140-150 g/m2. Table 9
• Table 10 illustrates that the reactivity of this adhesive system was higher than in example 2.
• the reference specimen having a merbau surface layer, was taken from normal production with the reference adhesive system.
• the test specimen H and I both having merbau surface layer were used.
• Samples for test of formaldehyde emission were also collected (specimen J, K, L). All the specimens were collected from different parquet boards.
• the gluing between the backing veneer and core layer seems to be better using the present adhesive system than the reference adhesive system.
• Test samples was cut in the correct dimensions for testing and conditioned in a conditioning room at 20 °C and a humidity of 65% in cleaned air for 5 to 6 days before testing in an desiccator in the applicant's laboratory.
• test specimens were pressed and heated in the standard production RF press.
• the RF time was adjusted to 19 seconds and the post press time was 10 seconds.
• the results of the bond quality tests are found in table 16, below.
• test samples from the test production were tested for formaldehyde emission according to JANS 16 and EN 717-1. The results are given in table 17 below. Before the test the test samples were conditioned in a chamber with 1 m purified air at 20 0 C and a relative humidity of 65%.
• Test samples of edge glued boards having a thickness of 21 mm were produced using a two component system according to the present invention.
• the test boards were compared with standard production edge glued boards from the same production facility.
• test boards were glued with a standard UF resin adhesive, Prefere® 4134 from Dynea OY and hardener B, being a combined hardener and modifier.
• the test boards were compared with boards glued with the UF resin adhesive Prefere® 4580 and hardener Prefere® 5109, both from Dynea OY.
• the test samples where produced from lamellas having a width of 45 mm, whereas the comparison sample was made from lamellas having a width of 42 mm.
• the adhesive part and the hardener part of the adhesive systems were mixed before application.
• Prefere® 4134 and Hardner J were mixed in a ratio of 100/50
• Prefere ® 4580 and Prefere® 5109 were mixed in a ratio of 78/22.
• After application of the glue the lamellas the lamellas were brought together and pressed at a temperature of 120 0 C.
• the two test samples were pressed for 100 and 121 seconds, respectively, whereas the comparison sample was pressed for 121 seconds.
• After pressing the two test samples were left for 30 minutes before they were wrapped into plastic.
• the comparison sample was wrapped into plastic after an unknown time (substantially longer than 30 minutes).
• the wrapped samples were transported to the applicants laboratory, cut into test pieces of 5 x 15 cm, each having two longitudinal glue lines and tested in a desiccator test according to JANS l ⁇ .The emission test results are found in table 18 below.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Adhesives Or Adhesive Processes (AREA)

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• 2005
  • 2005-10-05 NO NO20054572A patent/NO20054572L/no not_active Application Discontinuation
• 2006
  • 2006-10-05 AT AT06799568T patent/ATE556123T1/de active
  • 2006-10-05 WO PCT/NO2006/000343 patent/WO2007040410A1/en active Application Filing
  • 2006-10-05 EP EP06799568A patent/EP1945729B1/de not_active Revoked
  • 2006-10-05 PL PL06799568T patent/PL1945729T3/pl unknown
  • 2006-10-05 DK DK06799568.8T patent/DK1945729T3/da active
• 2008
  • 2008-05-02 NO NO20082037A patent/NO20082037L/no not_active Application Discontinuation

Non-Patent Citations (1)

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